0031004: Coding - eliminate warnings issued by gcc 9.1.0

0031004: Coding - eliminate warnings issued by gcc 9.1.0

Fixed -Wrestrict warning within OSD::SetSignal().

Fixed -Wdeprecated-copy warning by adding missing counterpart
in pair copy constructor / assignment operator or by removing trivial constructor.

AdvApp2Var_Node, AdvApp2Var_Patch are now declared as Handle.
AdvApp2Var_Iso is now passed by Handle.

Disabled operator= for TDF_Transaction and TDF_IDFilter.

Standard.cxx - fixed GCC version mischeck causing building failure with experimental GCC versions.

TopOpeBRepDS_EXPORT.cxx - fixed -Wmaybe-uninitialized warnings.